With the rapid advances in wireless communication networks, new wireless communication standards are often created to replace older obsolete standards. However, it often takes time to implement a new wireless network based on a new standard over a large physical area. Thus, it is often desirable to have a wireless terminal which can communicate with existing wireless networks as well as new wireless networks. Moreover, with the rapid growth of wireless computer data networks, it is often desirable to have a wireless terminal which can communicate with these networks to allow a user to browse the Internet or send and receive e-mail. Additionally, it may be useful to communicate with different wireless systems concurrently, so that a user may, for example, check e-mail on a wireless data network, while conducting a voice telephone call on a 2G wireless network.
Such wireless systems often use different time bases. For example, 2G GSM network uses a time base where frames have a duration of 4.615 milliseconds and are divided into 8 time slots. However, 3G WCDMA networks use a time base where frames have a duration of 10 milliseconds and are divided into 15 time slots. Events in the mobile terminal must be precisely timed and synchronized with respect to each of the wireless systems, regardless of whether the mobile terminal operates with one wireless system or operates concurrently two or more wireless systems.
Also, to maintain portability, wireless terminals are typically powered by batteries, where the time between recharges is an inverse function of the current drawn. Because it is desirable to allow the user to operate the wireless terminal for as long as possible between recharges, power management is an important consideration.